THERE are several features of interest in this new book on light by the headmaster of King Edward VII School, Sheffield. The method of presentation is historical, but only "in the sense that the discovery of facts and the development of ideas is presented as they occur historically". There is an unusually good account of Newton's experiments and of his deductions from the facts of observation. It is then pointed out how the mass of evidence grows until one theory fails and another has to take its place. The author adopts the convention as to signs which counts distances measured from the pole of a refracting surface in the same direction as the initial direction of the light positive, and the diagrams in the book are drawn with the incident light travelling from left to right so as to give agreement with the usual convention of coordinate geometry. Special mention must be made of the beautiful photographs supplied for the plates by Mr. J. W. Cottingham of Barnsley Grammar School and Dr. J. W. Mitchell of Repton School.
A Text Book on Light
By. Pp. x + 426 + 6 plates. (London, New York and Toronto: Longmans, Green and Co., Ltd., 1939.) 8s.